The invention relates to a device for folding a web of material.
U.S. Pat. No. 4,778,441 discloses an apparatus for folding a web of material. It consists essentially of an embossing roller which has concave and convex embossing elements as well as a matching counter roller. The paper to be embossed is guided between the two rollers.
Also disclosed in German OS 42 01 288 is a method and a machine for producing pleats on paper, filter material or other such media. This method also operates with a pair of notched rollers with indenting knives and anvils. Variable pleating can be produced by controlling them accordingly.
A device which produces zig-zag folded filter elements is disclosed in U.S. Pat. No. 3,514,354. Here two star rollers are provided which emboss and simultaneously fold the paper. Conveyor belts follow the star rollers to guide the pleated element into a shaping apparatus.
A disadvantage in the known embossing or pleating devices is that, in some of the materials to be processed, the embossing action is not sufficient to achieve a precise folded edge. It is especially disadvantageous that mechanical embossing by means of cylinders above a certain maximum speed results in poorer results as regards the embossing action.